A Time-Based CMOS Readout Circuit for Amperometric Biosensors

Miniaturization of electrochemical sensing devices for point-of-care, wearable and implantable diagnostics relies on CMOS potentiostat readouts that offer rapid and accurate test results. Conventional CMOS potentiostats are based on traditional analog blocks such as op amps and comparators, with a performance penalty in terms of power consumption and dynamic range. Time-based readout architectures offer unique advantages to achieve ultra-low power and low voltage operation without sacrificing small area and resolution. In this paper, we present the design of a CMOS potentiostat circuit with a current-mode time-based SAR ADC readout. The simulated results suggest that the readout channel can achieve an estimated energy efficiency of 1.5 pJ/bit from a 1.8 V supply. The proposed architecture can be readily scaled and programmed for a wide range of input currents, which makes it suitable for multiplexed multi-analyte systems.